Joule

[JGarcia]

How do you determine the number of Joules a bullet develops on impact?

For example, say you have a 123 grain bullet, travelling at 2198 FPS, or 670 MPS. A joule is equal to the kinetic energy of a two-kilgram mass moving at the speed of one meter per second.

a 123 grain bullet is .0079 kg, a 62 grain bullet is .004kg, when multiplied by the muzzle velocities of 670MPS, and 850 MPS respectively, I think that the amount of joules developed by each round should be 5.29 joules and 3.4 joules.

If I did this correctly, this should mean that the 7.62x39 has kinetic energy at the muzzle than the 5.56 NATO. This has absolutely nothing to do with accuracy, simply just kicking around the amount of energy delivered to a target.

I suppose the way to determine the amount of joules delivered to a target at a certain range, one must know the speed of the projectile at that range.

Also, what is the correct formula to determine PSI for the round striking a certain spot at a certain range, given the joules? Can you simply convert from joules to PSI? I think this would be handy to determine exactly how much barrier material one would need.

Had some free time. Did I do this correctly?

[Team Sergeant]

One joule is defined as the amount of energy exerted when a force of one newton is applied over a displacement of one meter.

One newton is the force required to cause a mass of one kilogram to accelerate at a rate of one meter per second squared in the absence of other force-producing effects.

Where did you come up with two kilograms?

Back to the drawing board.

[Jack Moroney (RIP)]

Originally posted by Team Sergeant
One joule is defined as the amount of energy exerted when a force of one newton is applied over a displacement of one meter.

The way I read this is that if I am standing one meter away from a target and throw a fig newton with enough force and hit him in the jewels he is going down. But I am from the old school and figure if I double tap the sucker I don't really have to worry about the physics involved.

Jack Moroney

[Team Sergeant]

Something I found for you, the conversion table has a foot pounds conversion for you.

The joule (J) is the SI unit of energy and work, and is defined as 1 kg·m2·s-2 = 1 N·m = 1 W·s. It is named in honour of the physicist James Prescott Joule.
One joule is the work required to exert a force of one newton for a distance of one metre, so the same quantity may be referred to as a newton metre. However, to avoid confusion the newton metre is usually used as a measure of torque, not energy. Another way of visualizing the joule is the work required to lift a mass of 102 g (e.g. a small apple) for one metre under the earth's gravity.

One joule is also the work done to produce power of one watt for one second, such as when somebody takes one second to lift the small apple mentioned above through one metre under the earth's gravity.

1 joule is equal to:

0.000,000,278 kilowatt hours
0.239 calories
0.000,948 British thermal units
0.738 foot pounds force
1 W·s (watt second)
1 N·m (newton metre)
23.7 foot poundals
10,000,000 ergs

http://www.fact-index.com/j/jo/joule.html

[Team Sergeant]

Originally posted by Jack Moroney
The way I read this is that if I am standing one meter away from a target and throw a fig newton with enough force and hit him in the jewels he is going down. But I am from the old school and figure if I double tap the sucker I don't really have to worry about the physics involved.

Jack Moroney

I agree Col. I am also of the understanding if you hit'em in the right spot it takes a lot less joules to knock them down.

TS

[Jack Moroney (RIP)]

Absolutely TS, couldn't agree more. I really wasn't trying to be a smart ass but I guess most of us have been subjected to all the best ballistics science from the folks that make ammo for us to do our jobs think is the right formula. You know, like the right combination of stuff for body armor until someone realizes that folks also get shot in the back and chest plates alone don't solve the problem. Or that a shot in the femoral artery where there is no armor is going to kill you just as quickly as a gut shot to the liver. Sort of the reason why head shots are sought and why "stingers" used up close and personal behind the ear will take you out . I have seen too many folks get bogged down with the science of killing when the nut cutting is all about putting the rounds on the target. But, I am glad someone a lot smarter than me has the time and patience to figure out what it takes to do the job so when I squeeze the trigger the round will do what it is designed to do without me having to crank up a calculator to make that adustment. Just a thought.

Jack Moroney

[JGarcia]

Actually TS, I got that definition here:

http://chemistry.about.com/library/g...tm?terms=joule

I was reading some article a while back (yesm, grunts read too) about the amount of joules certain armor can withstand. I forgot about it. Then recently bought a book, a biography about Maj. Boyd (inventor OODA). The book sort of inspired me to look into the science of things, as he did.

So, had some free time, and thought I'd compare the amount of joules a given weapon produces, using different bullets. In this case an AK 105 with a 12 inch barrel. I compared 7.62, and 5.56 fired from the same weapon, using the muzzle velocity info from charts by Kalishnikov.

I thought I had determined that it would be much more devastating to be shot with the 7.62 than the 5.56 at point blank range. But I will now have to go and do the math over, double check definitions of joules.

[The Reaper]

Originally posted by NG_M4_Shooter
Actually TS, I got that definition here:

http://chemistry.about.com/library/g...tm?terms=joule

I was reading some article a while back (yesm, grunts read too) about the amount of joules certain armor can withstand. I forgot about it. Then recently bought a book, a biography about Maj. Boyd (inventor OODA). The book sort of inspired me to look into the science of things, as he did.

So, had some free time, and thought I'd compare the amount of joules a given weapon produces, using different bullets. In this case an AK 105 with a 12 inch barrel. I compared 7.62, and 5.56 fired from the same weapon, using the muzzle velocity info from charts by Kalishnikov.

I thought I had determined that it would be much more devastating to be shot with the 7.62 than the 5.56 at point blank range. But I will now have to go and do the math over, double check definitions of joules.

Back to the drawing board.

Kinetic energy does not equate to energy transferred to the target, nor does it account for the wounding mechanism of the projectile's contruction.

In theory, a 6.8 oz. softball (193 grams) hitting you at 10 meters/second should damage you more than a 1 oz. icepick (28 grams) stabbing you at the same speed, but I doubt it.

This is far too complicated a topic to do justice to here, but suffice it to say that theoretical physics and terminal ballistics frequently contradict one another and are not likely to be reconciled by a layman.

TR

[JGarcia]

Just thought it would be interesting to kick around.

Hey TR, is mr Marenda (of recent step on penis fame over at socnet) still in the pipeline?

Are kinetic energy and joules the same?

[The Reaper]

Originally posted by NG_M4_Shooter
Just thought it would be interesting to kick around.

Hey TR, is mr Marenda (of recent step on penis fame over at socnet) still in the pipeline?

Are kinetic energy and joules the same?

It is interesting, more from a curiosity standpoint than a practical comparison.

I have no idea who the individual you reference is, nor would I discuss someone else's status in the course if I did.

A joule is a measure of kinetic energy if the object is moving. If the energy is stored (not moving), it is potential energy.

http://whatis.techtarget.com/definit...213564,00.html

TR